The CAsT corpus is a combination of corpora from MS MARCO [1]} and TREC CAR [2]}. MS MARCO includes an 8-million-passage corpus collected from Bing's QA system when it is originally released by Microsoft. Later, MS MARCO is augmented by a 3.3-million-document corpus constructed by fetching the full content of the URLs associated with those passages [3]}.
The TREC CAR corpus is constructed for the Complex Answer Retrieval Track and includes around 30 million passages collected from Wikipedia. In CAsT 2019 and CAsT 2020, the passage corpora are used and the task is passage retrieval. In CAsT 2021, the task is document retrieval and the MS MARCO document corpus is used.
